package exercise;

import java.util.Stack;

public class LC20 {
    public boolean isValid(String s) {
        Stack<Character> stack = new Stack<>();

        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch == '(' || ch == '{' || ch == '[') {
                stack.push(ch);
            } else {
                if (stack.isEmpty()) return false;
                char left = stack.pop();
                if (left == '(' && ch != ')' || left == '[' && ch != ']' || left == '{' && ch != '}') {
                    return false;
                }
            }
        }


        return stack.isEmpty();
    }
}
